The invention relates to a switchable differential drive, preferably for a motor vehicle drive.
EP 0 347 165 A2, published Dec. 20, 1989, describes a switchable differential drive which is used as a central differential of a four wheel drive vehicle. Also, this type of drive is used in the cases where different amounts of torque are distributed to the driveshafts in two different graduations. For these purposes, the differential is provided with three output shafts. One of two coaxially positioned output shafts is released and the other one is connected to an axle drive. A disadvantage of this design is a reversal in the direction of rotation.
The range of application of the present differential refers to motor vehicles driven by an electric motor, with only one axle being driven by the motor. In this application, the electric motor may be the only driving source of the vehicle. However, it may also be a vehicle with a hybrid drive in which case the electric motor is used in urban traffic and an internal combustion engine is used on the open road. In such a case, either the internal combustion engine drives the differential, with the electric motor disconnected, or it drives the second axle of the vehicle via a different differential of conventional design.
Considering the speeds of passenger cars, even if they are predominantly intended for urban traffic, the usable speed range of an electric motor rigidly connected to a differential is insufficient. Switchable control systems for the electric motor, which may improve the situation, are very expensive and not always technically satisfactory.